U.S. patent application number 11/647326 was filed with the patent office on 2007-07-12 for fuel vapor treatment apparatus, system having the same, method for operating the same.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Noriyasu Amano, Masao Kano, Shinsuke Takakura.
Application Number | 20070157908 11/647326 |
Document ID | / |
Family ID | 38231566 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070157908 |
Kind Code |
A1 |
Kano; Masao ; et
al. |
July 12, 2007 |
Fuel vapor treatment apparatus, system having the same, method for
operating the same
Abstract
A fuel vapor treatment apparatus connects with a fuel tank,
which produces fuel vapor to be purged into an intake passage of an
internal combustion engine through a purge passage. The fuel vapor
treatment apparatus includes a state measuring unit that includes a
measurement passage provided separately from the purge passage.
When the measurement passage is blocked from the intake passage,
the state measuring unit measures a state of fuel vapor by
detecting a physical quantity of the fuel vapor in the measurement
passage. The physical quantity is correlative to the state of fuel
vapor. The fuel vapor treatment apparatus further includes a
diagnosis unit for diagnosing a malfunction of at least one of
components of the state measuring unit.
Inventors: |
Kano; Masao; (Gamagori-city,
JP) ; Takakura; Shinsuke; (Kariya-city, JP) ;
Amano; Noriyasu; (Gamagori-city, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
NIPPON SOKEN, INC.
Nishio-city
JP
|
Family ID: |
38231566 |
Appl. No.: |
11/647326 |
Filed: |
December 29, 2006 |
Current U.S.
Class: |
123/520 |
Current CPC
Class: |
F02M 25/08 20130101 |
Class at
Publication: |
123/520 |
International
Class: |
F02M 25/08 20060101
F02M025/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 11, 2006 |
JP |
2006-3430 |
Claims
1. A fuel vapor treatment apparatus connecting with a fuel tank,
which produces fuel vapor to be purged into an intake passage of an
internal combustion engine through a purge passage, the fuel vapor
treatment apparatus comprising: a state measuring unit that
includes a measurement passage provided separately from the purge
passage, wherein when the measurement passage is blocked from the
intake passage, the state measuring unit measures a state of fuel
vapor by detecting a physical quantity of the fuel vapor in the
measurement passage, the physical quantity being correlative to the
state of fuel vapor, the fuel vapor treatment apparatus further
comprising: a diagnosis unit for diagnosing a malfunction of at
least one of components of the state measuring unit.
2. The fuel vapor treatment apparatus as defined in claim 1,
further comprising: a canister for adsorbing fuel vapor produced in
the fuel tank, wherein fuel vapor adsorbed to the canister is
purged into the intake passage through the purge passage, and fuel
vapor adsorbed in the canister flows through the measurement
passage.
3. The fuel vapor treatment apparatus as defined in claim 1,
wherein the state of fuel vapor is concentration of fuel vapor.
4. The fuel vapor treatment apparatus as defined in claim 1,
wherein the measurement passage includes a throttle therein, the
state measuring unit further includes: a first switching valve that
connects with the measurement passage, the first switching valve
adapted to communicating the throttle with selectively one of the
atmosphere and the purge passage; a flow generating unit for
generating fluid flow through the measurement passage; and a
pressure detecting unit for detecting pressure in the measurement
passage, wherein the pressure detecting unit detects an air
pressure when the following conditions are satisfied: the flow
generating unit operates; and the first switching valve
communicates the throttle with the atmosphere, wherein the pressure
detecting unit detects a mixture pressure of mixture including air
and fuel vapor when the following conditions are satisfied: purge
of fuel vapor into the intake passage through the purge passage is
suspended; and the first switching valve communicates the throttle
with the purge passage, wherein the state measuring unit controls a
quantity of fuel vapor to be purged into the intake passage on the
basis of the air pressure and the mixture pressure.
5. The fuel vapor treatment apparatus as defined in claim 4,
wherein the state measuring unit further includes: a concentration
calculating unit for calculating concentration of fuel vapor in the
mixture on the basis of the air pressure and the mixture
pressure.
6. The fuel vapor treatment apparatus as defined in claim 4,
further comprising: a second switching valve adapted to
communicating the flow generating unit with the purge passage, the
second switching valve adapted to blocking the flow generating unit
from the purge passage, wherein the first switching valve is
adapted to blocking among the throttle, the atmosphere, and the
purge passage from each other, the pressure detecting unit detects
reference pressure when the following conditions are satisfied: the
flow generating unit operates; the first switching valve
communicates the throttle with the atmosphere; and the second
switching valve blocks the flow generating unit from the purge
passage, wherein the pressure detecting unit detects first pressure
when the following conditions are satisfied: the first switching
valve blocks among the throttle, the atmosphere, and the purge
passage from each other; and the second switching valve
communicates the flow generating unit with the purge passage, the
fuel vapor treatment apparatus further includes: a leak check unit
for detecting leak in the fuel vapor treatment apparatus and the
fuel tank on the basis of the reference pressure and the first
pressure, wherein the diagnosis unit diagnoses a malfunction of the
second switching valve.
7. The fuel vapor treatment apparatus as defined in claim 4,
wherein when the pressure detecting unit is normal, the diagnosis
unit diagnoses a malfunction of any of the components other than
the pressure detecting unit on the basis of pressure detected by
the pressure detecting unit in the measurement of the state of fuel
vapor.
8. The fuel vapor treatment apparatus as defined in claim 4,
wherein the diagnosis unit diagnoses a malfunction of the pressure
detecting unit on the basis of a detection signal of the pressure
detecting unit immediately after starting the internal combustion
engine.
9. The fuel vapor treatment apparatus as defined in claim 4,
wherein the diagnosis unit diagnoses a malfunction of at least one
of the flow generating unit and the first switching valve on the
basis of pressure detected by the pressure detecting unit when the
following conditions are satisfied: the flow generating unit
operates; and the first switching valve blocks among the throttle,
the atmosphere, and the purge passage from each other.
10. The fuel vapor treatment apparatus as defined in claim 4,
wherein the diagnosis unit diagnoses a malfunction of at least one
of the flow generating unit and the first switching valve on the
basis of a change rate in pressure detected by the pressure
detecting unit when the following conditions are satisfied: the
flow generating unit operates; and the first switching valve
switches to block among the throttle, the atmosphere, and the purge
passage from each other.
11. The fuel vapor treatment apparatus as defined in claim 4,
wherein the diagnosis unit diagnoses a malfunction of at least one
of the flow generating unit, the first switching valve, and the
throttle on the basis of pressure detected by the pressure
detecting unit when the following conditions are satisfied: the
flow generating unit operates; and the first switching valve
communicates the throttle with the atmosphere.
12. The fuel vapor treatment apparatus as defined in claim 4,
wherein the diagnosis unit diagnoses a malfunction of at least one
of the flow generating unit and the first switching valve on the
basis of a change rate in pressure detected by the pressure
detecting unit when the following conditions are satisfied: the
flow generating unit operates; and the first switching valve
switches to communicate the throttle with the atmosphere.
13. The fuel vapor treatment apparatus as defined in claim 4,
wherein the diagnosis unit diagnoses a malfunction of at least one
of the flow generating unit, the first switching valve, and the
throttle on the basis of pressure detected by the pressure
detecting unit when the following conditions are satisfied: the
flow generating unit operates; and the first switching valve
communicates the throttle with the purge passage.
14. The fuel vapor treatment apparatus as defined in claim 4,
further comprising: a purge valve that is provided in the purge
passage for controlling a quantity of fuel vapor to be purged into
the intake passage, wherein the diagnosis unit diagnoses a
malfunction of at least one of the purge valve and the first
switching valve on the basis of pressure detected by the pressure
detecting unit when the following conditions are satisfied: the
first switching valve communicates the throttle with the purge
passage; and fuel vapor is purged into the intake passage.
15. The fuel vapor treatment apparatus as defined in claim 4,
wherein the diagnosis unit diagnoses a malfunction of the first
switching valve on the basis of pressure detected by the pressure
detecting unit when the following conditions are satisfied: the
first switching valve blocks the throttle from the purge passage;
the first switching valve communicates the throttle with the
atmosphere; and fuel vapor is purged into the intake passage.
16. The fuel vapor treatment apparatus as defined in claim 6,
wherein the diagnosis unit diagnoses a malfunction of the second
switching valve on the basis of pressure detected by the pressure
detecting unit when the following conditions are satisfied: the
first switching valve communicates the throttle with the purge
passage; and fuel vapor is purged into the intake passage.
17. The fuel vapor treatment apparatus as defined in claim 6,
wherein the diagnosis unit diagnoses a malfunction of the second
switching valve on the basis of pressure detected by the pressure
detecting unit when the following conditions are satisfied: fuel
vapor is purged into the intake passage; the first switching valve
blocks the throttle from the purge passage; and the first switching
valve communicates the throttle with the atmosphere.
18. The fuel vapor treatment apparatus as defined in claim 6,
wherein the diagnosis unit diagnoses a malfunction of at least one
of the flow generating unit, the first switching valve, and the
second switching valve on the basis of pressure detected by the
pressure detecting unit when the following conditions are
satisfied: the flow generating unit operates; and the second
switching valve communicates the flow generating unit with the
purge passage.
19. The fuel vapor treatment apparatus as defined in claim 6,
further comprising: a purge valve that is provided in the purge
passage for controlling a quantity of fuel vapor purged into the
intake passage, wherein the pressure detecting unit detects second
pressure when the following conditions are satisfied: the flow
generating unit operates; the second switching valve communicates
the flow generating unit with the purge passage; and the purge
valve communicates therein, wherein the diagnosis unit diagnoses a
malfunction of the purge valve on the basis of the second
pressure.
20. A fuel vapor treatment system for an internal combustion engine
connecting with a fuel tank, the internal combustion engine drawing
air through an intake passage, the fuel vapor treatment system
comprising: a fuel vapor treatment apparatus that includes a purge
passage through which fuel vapor produced in the fuel tank is
purged into the intake passage, wherein the fuel vapor treatment
apparatus further includes a measurement passage trough which fuel
vapor flows from the fuel tank, the fuel vapor treatment apparatus
further includes a sensing unit for detecting a state of the fuel
vapor in the measurement passage when the measurement passage is
blocked from the intake passage, and the sensing unit diagnoses a
malfunction of the fuel vapor treatment apparatus in accordance
with the state of the fuel vapor.
21. A method for operating a fuel vapor treatment system including
a fuel vapor treatment apparatus for purging fuel vapor produced in
a fuel tank into an intake passage of an internal combustion engine
through a purge passage, the method comprising: introducing fuel
vapor from the fuel tank into a measurement passage in a condition
where the measurement passage is blocked from the intake passage;
measuring a state of the fuel vapor in the measurement passage by
detecting a physical quantity correlative to the state of fuel
vapor; and diagnosing a malfunction of at least one of components
constructing the fuel vapor treatment apparatus in accordance with
the state of fuel vapor.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and incorporates herein by
reference Japanese Patent Application No. 2006-3430 filed on Jan.
11, 2006.
FIELD OF THE INVENTION
[0002] The present invention relates to a fuel vapor treatment
apparatus. The present invention further relates to a fuel vapor
treatment system having the fuel vapor treatment apparatus. The
present invention further relates to a method for operating the
fuel vapor treatment system.
BACKGROUND OF THE INVENTION
[0003] A fuel vapor treatment apparatus directly purges fuel vapor,
which is produced in a fuel tank, into an intake passage of an
internal combustion engine. Alternatively, a fuel vapor treatment
apparatus temporarily adsorbs fuel vapor to an adsorbent of a
canister and then purges the adsorbed fuel vapor into the intake
passage. In the fuel vapor treatment apparatus according to
JP-A-H5-18326 or JP-A-H6-101534, a fuel vapor concentration in a
mixture to be purged into the intake passage is measured as a fuel
vapor state prior to the purge. Concretely, the flow rate or
density of the mixture is detected in a purge passage through which
the mixture is purged into the intake passage. In addition, the
flow rate or density of air is detected in an atmospheric passage,
which opens to the atmosphere.
[0004] The fuel vapor concentration is measured in accordance with
the ratio between the detection results of the purge passage and
the atmospheric passage. In the above structure, negative pressure
in the intake passage is applied to each of the passages, and the
mixture or air flows through the corresponding passage, whereby the
flow rate or density is detected. When a pulsation occurs in
negative pressure through the intake passage, the flow rate or
density fluctuates, and the measurement accuracy of the fuel vapor
concentration decreases. Besides, when negative pressure of the
intake passage is small, the flow rate of the mixture or air in the
corresponding passage decreases. Consequently, the detection of the
flow rate or density becomes difficult.
[0005] Fuel vapor produced in the fuel tank may flow into a
measurement passage separate from the purge passage, when the
measurement passage is blocked from the intake passage. Here, the
fuel vapor concentration is measured in such a way that a physical
quantity such as pressure or flow rate correlating to the fuel
vapor concentration is detected in the measurement passage.
Accordingly, fuel vapor or air flows through the measurement
passage irrespective of the fluctuation of negative pressure of the
intake passage, and the fuel vapor concentration may be precisely
measured.
[0006] Fuel vapor is purged into the intake passage on the basis of
the measured fuel-vapor concentration. A quantity of fuel injected
from a fuel injection valve is set in accordance with a quantity of
fuel vapor, which is to be purged. In this regard, when a
malfunction occurs in any of components for measuring the fuel
vapor state, the measurement cannot be accurately performed. As a
result, the quantity of fuel injection cannot be appropriately set,
and consequently, an actual air/fuel ratio may deviate from a
target air/fuel ratio.
SUMMARY OF THE INVENTION
[0007] The present invention addresses the above disadvantage.
[0008] According to one aspect of the present invention, a fuel
vapor treatment apparatus connects with a fuel tank, which produces
fuel vapor to be purged into an intake passage of an internal
combustion engine through a purge passage. The fuel vapor treatment
apparatus includes a state measuring unit that includes a
measurement passage provided separately from the purge passage.
When the measurement passage is blocked from the intake passage,
the state measuring unit measures a state of fuel vapor by
detecting a physical quantity of the fuel vapor in the measurement
passage. The physical quantity is correlative to the state of fuel
vapor. The fuel vapor treatment apparatus further includes a
diagnosis unit for diagnosing a malfunction of at least one of
components of the state measuring unit.
[0009] According to another aspect of the present invention, a fuel
vapor treatment system is used for an internal combustion engine
connecting with a fuel tank. The internal combustion engine draws
air through an intake passage. The fuel vapor treatment system
includes a fuel vapor treatment apparatus that includes a purge
passage through which fuel vapor produced in the fuel tank is
purged into the intake passage. The fuel vapor treatment apparatus
further includes a measurement passage through which fuel vapor
flows from the fuel tank. The fuel vapor treatment apparatus
further includes a sensing unit for detecting a state of the fuel
vapor in the measurement passage when the measurement passage is
blocked from the intake passage. The sensing unit diagnoses a
malfunction of the fuel vapor treatment apparatus in accordance
with the state of the fuel vapor.
[0010] According to another aspect of the present invention, a
method is used for operating a fuel vapor treatment system, which
includes a fuel vapor treatment apparatus for purging fuel vapor
produced in a fuel tank into an intake passage of an internal
combustion engine through a purge passage. The method includes
introducing fuel vapor from the fuel tank into a measurement
passage in a condition where the measurement passage is blocked
from the intake passage. The method further includes measuring a
state of the fuel vapor in the measurement passage by detecting a
physical quantity correlative to the state of fuel vapor. The
method further includes diagnosing a malfunction of at least one of
components constructing the fuel vapor treatment apparatus in
accordance with the state of fuel vapor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The above and other objects, features and advantages of the
present invention will become more apparent from the following
detailed description made with reference to the accompanying
drawings. In the drawings:
[0012] FIG. 1 is a schematic view showing a fuel vapor treatment
apparatus according to a first embodiment;
[0013] FIG. 2 is a schematic view showing a flow passage when
cutoff pressure of a pump is detected in the fuel vapor treatment
apparatus;
[0014] FIG. 3 is a schematic view showing a flow passage when air
pressure is detected in the fuel vapor treatment apparatus;
[0015] FIG. 4 is a schematic view showing a flow passage when
pressure of mixture including air and fuel vapor is detected in the
fuel vapor treatment apparatus;
[0016] FIG. 5 is a schematic view showing a flow passage when
mixture is purged from both first and second canisters in the fuel
vapor treatment apparatus;
[0017] FIG. 6 is a schematic view showing a flow passage when
mixture is purged from the first canister in the fuel vapor
treatment apparatus;
[0018] FIG. 7 is a schematic view showing a flow passage when
reference pressure is detected in the fuel vapor treatment
apparatus;
[0019] FIG. 8 is a schematic view showing a flow passage when a
leak check operation is performed and a purge valve blocks therein,
in the fuel vapor treatment apparatus;
[0020] FIG. 9 is a schematic view showing a flow passage when the
leak check operation is performed and the purge valve communicates
therein, in the fuel vapor treatment apparatus;
[0021] FIG. 10 is a time chart showing an operation of the fuel
treatment apparatus;
[0022] FIG. 11 is a time chart showing an operation for measuring a
fuel vapor concentration in the fuel vapor treatment apparatus;
[0023] FIG. 12 is a time chart showing an operation for purging
mixture in the fuel vapor treatment apparatus;
[0024] FIG. 13 is a time chart showing the leak check operation in
the fuel vapor treatment apparatus;
[0025] FIG. 14 is a time chart showing an operation of a fuel vapor
treatment apparatus according to a modified embodiment;
[0026] FIG. 15 is a schematic view showing solenoid valves for a
fuel treatment apparatus according to a second embodiment;
[0027] FIG. 16 is a schematic view showing solenoid valves for a
fuel treatment apparatus according to a third embodiment;
[0028] FIG. 17 is a schematic view showing a fuel vapor treatment
apparatus, according to a fourth embodiment; and
[0029] FIG. 18 is a time chart showing an operation according to
the fourth embodiment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
First Embodiment
[0030] In an example shown in FIG. 1, a fuel vapor treatment
apparatus 30 is provided to an internal combustion engine 10 of a
vehicle. The engine 10 may be a gasoline engine, which generates
power by combusting gasoline accommodated in a fuel tank 32. A fuel
injection valve 16 for controlling a fuel injection quantity, a
throttle valve 18 for controlling a flow rate of intake air, and
the like are provided in an intake passage 14 of the engine 10. An
air/fuel ratio sensor 22 for detecting an air/fuel ratio, and the
like are provided in the exhaust passage 20
[0031] Next, an operation of the fuel vapor treatment apparatus 30
is described. Fuel vapor is produced in the fuel tank 32, and the
fuel vapor is once adsorbed to a first canister 34. The fuel vapor
adsorbed to the first canister 34 is purged into the intake passage
14. The fuel tank 32 connects with the first canister 34 through a
passage 100. Fuel vapor, which is produced in the fuel tank 32,
passes through the passage 100, and the fuel vapor is adsorbed to
an adsorbent such as an activated charcoal in the first canister
34. When a purge valve 36 communicates therein, fuel vapor adsorbed
to the first canister 34 passes through a purge passage 102, so
that the fuel vapor is drawn by negative pressure in the intake
passage 14, and is purged into the intake passage 14 the downstream
of the throttle valve 18. In a state shown in FIG. 1, the first
canister 34 communicates with the atmosphere through a passage 104,
a solenoid valve 46, and a filter 38. The first canister 34
connects with a solenoid valve 44 through a passage 110, which
communicates with the purge passage 102.
[0032] The fuel vapor treatment apparatus 30 detects a fuel vapor
state indicated by a fuel vapor concentration in a mixture of air
and fuel vapor, which is purged into the intake passage 14. The
fuel vapor treatment apparatus 30 controls the purge valve 36,
thereby controlling a fuel vapor quantity to be purged into the
intake passage 14, so that the fuel vapor treatment apparatus 30
controls the fuel injection quantity of the fuel injection valve 16
in accordance with the measured fuel-vapor concentration.
[0033] A state measuring unit measures the concentration of fuel
vapor, which is purged from the first canister 34 into the intake
passage 14 through the purge valve 36. The state measuring unit
includes a pump 42, the solenoid valve 44, a pressure sensor 50, a
control unit (ECU) 60, and a measurement passage 112. The ECU 60
serves as a concentration calculating unit, a diagnosis unit, and a
leak check unit. The ECU 60 controls the fuel injection valve 16,
the throttle valve 18, the purge valve 36, the pump 42, and
solenoid valves 44 and 46.
[0034] A throttle 40 is provided in the measurement passage 112.
The solenoid valve 44 is provided in the measurement passage 112
connecting with the throttle 40. The solenoid valve 44 serves as a
first switching valve.
[0035] A second canister 48, the pump 42, and a filter 39 are
provided in the measurement passage 112 on the opposite side of the
solenoid valve 44 with respect to the throttle 40. The second
canister 48, the pump 42, and the filter 39 are arranged in this
order from the throttle 40. A passage 114 connects part of the
measurement passage 112, which is located between the pump 42 and
the filter 39, with the solenoid valve 44 on the opposite side of
the throttle 40. One end of the passage 114 opens to the atmosphere
through the filter 39.
[0036] The solenoid valve 44 operates to switch one of three
positions including communication between the throttle 40 and the
passage 114, communication between the throttle 40 and the passage
110, and blockade between the throttle 40 and both the passages 110
and 114, for example. When electricity supply to the solenoid valve
44 is terminated, the solenoid valve 44 maintains the throttle 40
and the passage 114 in communication, so that and the solenoid
valve 44 communicate the throttle 40 with the atmosphere through
the passage 114, for example. The solenoid valve 46 serves as a
second switching valve.
[0037] As shown in FIG. 1, when electricity supply to the solenoid
valve 46 is terminated, the solenoid valve 46 communicates the
passage 104 with the atmosphere through the filter 38, so that the
first canister 34 communicates with the atmosphere through the
passage 104 and the solenoid valve 46.
[0038] In this condition, when the purge valve 36 communicates
therein in this state, fuel vapor adsorbed to the first canister 34
is purged to the downstream of the throttle valve 18 through the
purge passage 102 by negative pressure in the intake passage 14.
When the fuel vapor treatment apparatus 30 is in a leak check mode,
the solenoid valve 46 is supplied with electricity to communicate a
passage 106 with the passage 104, thereby communicating the pump 42
with the first canister 34. The passage 106 communicates with part
of the measurement passage 112 between the pump 42 and the second
canister 48. When the passages 106 communicate with the passage
104, the pump 42 operates to reduce pressure in the first canister
34 and the passages in the fuel vapor treatment apparatus 30, so
that a leak check operation is performed. The pump 42 serves as a
flow generating unit. The pump 42 also serves as a pressure
generating unit.
[0039] The second canister 48 is provided in the measurement
passage 112 between the throttle 40 and the pump 42. Likewise to
the first canister 34, the second canister 48 accommodates an
adsorbent such as an activated charcoal therein.
[0040] When the solenoid valve 44 communicates the measurement
passage 112 with the passage 110, the pump 42 operates to reduce
pressure through the measurement passage 112, so that fuel vapor
adsorbed to the first canister 34 is drawn into the measurement
passage 112. Thus, the mixture including air and fuel vapor flows
into the second canister 48 after passing through the throttle 40,
so that the second canister 48 adsorbs fuel vapor, thereby removing
the fuel vapor from the mixture.
[0041] In this fuel vapor treatment apparatus 30, the second
canister 48 is provided between the pump 42 and the throttle 40 so
as to remove fuel vapor from the mixture after passing through the
throttle 40. When the mixture including air and fuel vapor passes
through the throttle 40, the detection pressure in this structure
is greater than the detection pressure in a structure where the
second canister 48 is not provided. Therefore, the air pressure
P.sub.AIR, when the air passes through the throttle 40, and the
mixture pressure P.sub.GAS, when the mixture including air and fuel
vapor passes through the throttle 40, have a greater differential
value therebetween by providing the second canister 48 between the
pump 42 and the throttle 40. Accordingly, a sufficiently large
detection gain G can be ensured for the pressure resolution of the
pressure sensor 50, and the relative detection accuracy of the
mixture pressure P.sub.GAS to the air pressure P.sub.AIR, in turn,
the measurement accuracy of the fuel vapor concentration is
enhanced.
[0042] The pressure sensor 50 connects with the part of the
measurement passage 112 between the pump 42 and the second canister
48. This pressure sensor 50 is, for example, a differential
pressure sensor, which detects the differential pressure between
the atmospheric pressure and pressure in the measurement passage
112 in the passage between the pump 42 and the second canister 48.
That is, the pressure sensor 50 detects the differential pressure
in the passage between the pump 42 and the throttle 40; The
pressure sensor 50 serves as a pressure detecting unit.
[0043] The detection pressure, which the pressure sensor 50 detects
during the operation of the pump 42, is substantially equal to
differential pressure across the throttle 40, when the solenoid
valve 44 maintains the throttle 40 in communication with the
atmosphere. When the solenoid valve 44 blocks the throttle 40 from
both the passages 110 and 114, the measurement passage 112 is
closed on the suction side of the pump 42. The detection pressure
of the pressure sensor 50 during the operation of the pump 42
becomes substantially equal to the cutoff pressure of the pump
42.
[0044] As shown in FIG. 10, the time chart successively indicates
the respective stages of standby (A), the measurement of the fuel
vapor concentration (B-E), the purge of fuel vapor (F-G), and the
leak check operation (J-L) after the turn-ON of an ignition key.
The fuel vapor concentration measurement, the purge, the leak check
operation, and a malfunction diagnosis, described below, are
processed in such a way that the ECU 60 executes control programs
stored in a ROM, an EEPROM, and the like of the ECU 60. When the
ECU 60 determines any of the components for measuring the fuel
vapor concentration to malfunction, the measurement of the fuel
vapor concentration and the diagnostic process are desirably
stopped, the purge valve (PV) 36 is desirably closed, and purge of
fuel vapor into the intake passage 14 is desirably stopped. When
the purge of fuel vapor is stopped, the injection quantity of the
fuel injection valve 16 may be adjusted to produce the target
air/fuel ratio on the basis of an actual air/fuel ratio detected by
the air/fuel ratio sensor 22. The causes of malfunctions in the
following diagnostic process are examples.
[0045] The stage A in FIGS. 10 and 11 is immediately after the
start of the engine 10 since the turn-ON of the ignition key. At
the stage A, the pump 42 is stopped, and the solenoid valves 44 and
46 (SV 44, 46) are in the state shown in FIG. 1, so that the
measurement passage 112 communicates with the atmosphere. In this
state, the output of the pressure sensor 50 is diagnosed. When an
output voltage of the pressure sensor 50 is outside a range in the
normal operation of this pressure sensor 50, it is determined that
the pressure sensor 50 is disconnected or short-circuited. In this
state, the malfunction of the fuel vapor treatment apparatus is
notified to the driver of the vehicle by, for example, lighting up
a warning lamp or producing a warning sound. In order to notify the
malfunction portion, a malfunction flag may be set in a memory such
as the EEPROM of the ECU 60 so as to turn ON the set the
malfunction flag of the pressure sensor 50.
[0046] When the voltage of the pressure sensor 50 is within the
normal range, so that a pressure P indicated by the voltage of the
pressure sensor 50 is in P.sub.0-K0.ltoreq.P.ltoreq.P.sub.0+K0 with
respect to the atmospheric pressure P.sub.0, the pressure sensor 50
is determined to be normal. Alternatively, when the pressure P is
not in P.sub.0-K0.ltoreq.P.ltoreq.P.sub.0+K0, the pressure sensor
50 is determined to malfunction. When the pressure sensor 50 is
determined to be normal at the stage A, the pressure sensor 50 is
assumed to be normal in the following diagnosis.
[0047] When the pressure P indicated by the pressure sensor 50 is
low where P<P.sub.AL, it is determined that the pressure P is
reduced due to operating the pump 42 even supplying electricity to
the pump 42 is terminated. In this situation, the malfunction is
caused since the pump 42 is improperly in its ON state.
[0048] The stage A is in the standby state. At the stage A, when
the engine speed exceeds several hundred rpm, or water temperature
exceeds a predetermined temperature, for example, it is determined
that the condition for detecting fuel vapor concentration is
satisfied. When the ambient temperature of the fuel tank 32 is low,
fuel vapor is hardly produced in the fuel tank 32. Except
immediately after the start, the condition for detecting fuel vapor
concentration may be satisfied when the ambient temperature of the
fuel tank 32 increases such that fuel vapor is produced in the fuel
tank. When the condition for detecting fuel vapor concentration is
satisfied, the stage A shifts to the stage B, at which the fuel
vapor concentration is measured.
[0049] At the stage B in FIGS. 10 and 11, the solenoid valve 44 is
operated to be in the state shown in FIG. 2, thereby blocking the
throttle 40 from both the passages 110 and 114, and the pump 42 is
operated. In this state, the suction side of the pump 42 is blocked
via the throttle 40, so that the pressure sensor 50 detects the
cutoff pressure P.sub.C of the pump 42. When the pressure P
indicated by the pressure sensor 50 is in
P.sub.CH.ltoreq.P.ltoreq.P.sub.CL with respect to the predetermined
cutoff pressure P.sub.C, the pressure sensor 50 is determined to be
normal. When the pressure P corresponds to P.ltoreq.P.sub.CL, the
pressure sensor 50 may be determined normal. The P.sub.CH is on the
side of negative in pressure with respect to the P.sub.CL. That is,
the P.sub.CH is less than the P.sub.CL in absolute pressure.
[0050] When P.sub.0-K0.ltoreq.P.ltoreq.P.sub.0+K0 is satisfied, it
is determined that the pressure does not change since the stage A.
That is, the situation is determined to malfunction in which the
pump 42 is not operated even though being supplied with
electricity. When the pressure P is not in
P.sub.CH.ltoreq.P.ltoreq.P.sub.CL, the pump 42 is determined to
malfunction. Alternatively, when the pressure P is not in
P.sub.CH.ltoreq.P.ltoreq.P.sub.CL but is around the predetermined
air pressure P.sub.AIR, it is determined that the throttle 40
communicates with the atmosphere through the passage 114, even
though the solenoid valve 44 is operated from the stage A shown in
FIG. 1 to the state shown in FIG. 2. In this case, the solenoid
valve 44 may be determined to malfunction.
[0051] When the absolute value of a pressure decreasing rate
.DELTA.P/.DELTA.t the shift from the stage A to the stage B is
small, or where a period T1 in which pressure P reaches the cutoff
pressure P.sub.C is longer than a predetermined period, it may be
determined to malfunction. In this case, the suction performance of
the pump 42 may be insufficient, or the passage 106 may partly
communicate with the atmosphere due to incompletely blockade of the
solenoid valve 46. That is, at least one of the pump 42 and the
solenoid valve 46 is determined to malfunction.
[0052] When any malfunction is not caused at the stage B where the
cutoff pressure P.sub.C is detected, the stage B shifts to the next
stage C at which air pressure is detected. Specifically, the pump
42 is operated, and the solenoid valves 44 and 46 are operated to
be in the state shown in FIG. 3, in which only air flows through
the throttle 40. The pressure sensor 50 detects the air pressure
P.sub.AIR. When the pressure P indicated by the pressure sensor 50
is in P.sub.AH.ltoreq.P.ltoreq.P.sub.AL with respect to the
predetermined air pressure P.sub.AIR, the pressure is determined to
be normal.
[0053] When P>P.sub.AL is satisfied, the pressure P is
determined to be excessively high. In this case, the cause of the
malfunction is determined that the choking diameter in the throttle
40 becomes large, alternatively, the suction performance of the
pump 42 is insufficient, alternatively, the passage 106 is not
properly blocked by the solenoid valve 46. That is, at least one of
the throttle 40, the pump 42, and the solenoid valve 46 is
determined to malfunction.
[0054] When P<P.sub.AH is satisfied, the pressure P is
excessively low. In this case, the cause of the malfunction is
determined that the choking diameter of the throttle 40 becomes
small, alternatively, the solenoid valve 44 does not communicate
the measurement passage 112 with the passage 114 even though being
operated. That is, at least either of the throttle 40 and the
solenoid valve 44 is determined to malfunction.
[0055] When a differential pressure |P.sub.C-P.sub.AIR| at the
shift from the stage B to the stage C is excessively small, it is
determined to be abnormal that the solenoid valve 44 is not
properly operated from the state shown in FIG. 2 to the state shown
in FIG. 3.
[0056] As shown in FIG. 11, when the absolute value of a pressure
increasing rate .DELTA.P/.DELTA.t the shift from the stage B to the
stage C is small, or where the pressure P reaches the air pressure
P.sub.AIR is longer than a predetermined period, it is determined
to be malfunction. In this case, the suction performance of the
pump 42 is not sufficient, alternatively the throttle 40 does not
properly communicate with the passage 114 through the solenoid
valve 44. That is, at least one of the pump 42 and the solenoid
valve 44 is determined to malfunction.
[0057] When any malfunction is not caused at the stage C where the
air pressure P.sub.AIR is detected, the stage C shifts to the next
stage D at which the pressure of the mixture is detected.
[0058] At the stage D, the pump 42 is operated, and the solenoid
valves 44 and 46 are operated to be in the state shown in FIG. 4,
so that the mixture including air and fuel vapor flows through the
throttle 40. In this state, the pressure sensor 50 detects the
mixture pressure P.sub.GAS. When the pressure P indicated by the
pressure sensor 50 lies in
P.sub.C-.alpha.<P<P.sub.AIR+.alpha., it is determined to be
normal.
[0059] When P>P.sub.AIR+.alpha. or P.sub.C-.alpha.>P is
satisfied, it is determined that at least one component in the
passages of thick solid lines depicted in FIG. 4 such as the
solenoid valves 44 and 46, the throttle 40 the pump 42 is
malfunction.
[0060] When any malfunction is not detected at the above stages
A-D, the ECU 60 calculates the fuel vapor concentration in
accordance with the cutoff pressure P.sub.C, the air pressure
P.sub.AIR, and the mixture pressure P.sub.GAS. Subsequently, the
opening defined in the purge valve (PV) 36 and the fuel injection
quantity of the fuel injection valve 16 are set so as to produce
the target air/fuel ratio. The cutoff pressure P.sub.C, the air
pressure P.sub.AIR and the mixture pressure P.sub.GAS correspond to
physical quantities.
[0061] When the fuel vapor concentration is normally measured and
where the purge condition is satisfied, as shown in FIGS. 10 and
12, the stage E waiting for the purge is shifted to the stages F
and G executing the purge. At the stages F and G, fuel vapor
adsorbed to the first canister 34 is purged into the intake passage
14.
[0062] At the stage F, the pump 42 stops, the purge valve 36 opens
to communicate therein, and the solenoid valves 44 and 46 are
operated to be in the states shown in FIG. 5. In this condition,
fuel vapor is purged from both the first canister 34 and the second
canister 48. When, at the stage F, the pressure P of the pressure
sensor 50 is reduced by negative pressure in the intake passage 14,
so that P.sub.PH.ltoreq.P.ltoreq.P.sub.PL is satisfied, it is
determined to be normal.
[0063] When P>P.sub.PL is satisfied, it is determined to be
malfunction that pressure in the measurement passage 112 is not
properly reduced. The cause of this malfunction is, for example,
that the purge valve 36 may not be opened even though being
supplied with electricity, or that the solenoid valve 44 does not
communicate the throttle 40 with the passage 110.
[0064] When P<P.sub.PH is satisfied, it is determined to be
malfunction that the pressure P of the pressure sensor 50
improperly decreases since the solenoid valve 46 does not block the
first canister 34 from the pump 42.
[0065] When the output of the air/fuel ratio sensor 22 indicates a
value on a rich side beyond the predetermined range of the target
air/fuel ratio during the purge, it is determined that at least one
of the components including the air/fuel ratio sensor 22 and the
fuel injection valve 16 to malfunction.
[0066] In an operation where fuel vapor is purged from only the
first canister 34, the pump 42 stops, and the purge valve 36 opens
to communicate therein, and the solenoid valves 44 and 46 are
operated to be in the states shown in FIG. 6. The purge process
here is the same as the process of a fuel vapor treatment
apparatus, which does not use the second canister 48. As shown in
FIG. 6, at the stage G, the measurement passage 112 opens to the
atmosphere. Therefore, when P.sub.0-K0.ltoreq.P.ltoreq.P.sub.0+K0
is satisfied, it is determined to be normal. When P<P.sub.0-K0
is satisfied, it is determined to malfunction that the throttle 40
communicates with the purge passage 102 through the solenoid valve
44, or that the passages 104 and 106 communicate with each other
through the solenoid valve 46.
[0067] When the leak check condition is satisfied, the ECU 60
executes the leak check operation after the turn-OFF of the
ignition key. First, as shown in FIGS. 10 and 13, a reference
pressure P.sub.Ref is detected at the stage J. At the stage J, the
pump 42 is operated, and the solenoid valves 44 and 46 are in the
states shown in FIG. 7, so that only air flows through the throttle
40. The connection among the passages in the stage J is the same as
the connection in the stage C refer to FIG. 3, in which the air
pressure P.sub.AIR is detected for the fuel vapor concentration
measurement. The diagnosis operation in the stage J is the same as
the diagnosis operation in the stage C.
[0068] When any malfunction is not caused at the stage J, the
internal pressure check of the fuel vapor treatment apparatus 30
including the fuel tank 32 is performed at the next stage K. As
shown in FIG. 8, at the stage K in FIGS. 10 and 13, the purge valve
36 closes to block therein, the pump 42 is operated, and the
solenoid valves 44 and 46 are in the states in FIG. 8.
[0069] When the pressure P indicated by the pressure sensor 50 does
not change even supplying electricity to the pump 42, the pump 42
is determined to malfunction.
[0070] When the pressure P changes, but where the pressure P is
higher than the reference pressure P.sub.Ref and is close to the
atmospheric pressure, the situation is determined to malfunction.
In this condition, a hole, which is larger in diameter than the
throttle 40, may open in the fuel vapor treatment apparatus 30
including the fuel tank 32, or any of the components of the fuel
vapor treatment apparatus 30 for performing the leak check
operation may malfunction. In this case, the malfunction may be,
for example, at least one of that the suction performance of the
pump 42 is insufficient, that the solenoid valve 46 sticks in an
intermediate position therein, that the passage 106 communicates
with the atmosphere through the throttle 40, and that the solenoid
valve 46 leaks.
[0071] When the pressure P decreases to the reference pressure
P.sub.Ref in a short time in the same manner as at the stage J, it
is determined that the solenoid valve 46 remains in the state of
FIG. 7, even though being supplied with electricity. That is, the
solenoid valve 46 is determined to malfunction.
[0072] When any malfunction is not caused at the stage K, an
malfunction of the purge valve 36 is diagnosed at the next stage L
shown in FIGS. 10 and 13.
[0073] As shown in FIG. 9, the purge valve 36 is supplied with
electricity, thereby opening to communicate therein, so that the
stage K shown in FIG. 8 shifts to stage L shown in FIG. 9. When the
purge valve 36 normally communicates therein, the purge passage 102
communicates with the intake passage 14, so that the pressure P of
the pressure sensor 50 increases to around the atmospheric pressure
P.sub.0. When the pressure P of the pressure sensor 50 remains
unchanged from that in the stage K, it is determined that the purge
valve 36 does not communicate therein, even though being supplied
with electricity. That is, the purge valve 36 is determined to
malfunction.
[0074] When a malfunction is caused in any of the components for
measuring the fuel vapor concentration, the malfunction is
desirably notified to the driver of the vehicle by lighting up the
warning lamp or producing the warning sound, for example. A
malfunction flag may be set for every component in the EEPROM or
the like of the ECU 60, and may be turned ON so as to specify the
malfunction portion.
[0075] In the above structure, the components for measuring the
fuel vapor concentration serve also as components for performing
the leak check operation, so that additional components for
performing the leak check operation can be reduced.
[0076] The pressure sensor 50 is diagnosed, and thereafter, when
the pressure sensor 50 is normal, the other components for
measuring the fuel vapor concentration are diagnosed on the basis
of the detection signal of the pressure sensor 50. Therefore,
additional components or modules for performing the malfunction
diagnoses are not needed.
[0077] The fuel vapor treatment apparatus 30 has the measurement
passage 112 separately from the purge passage 102 through which
fuel vapor produced in the fuel tank 32 is purged into the intake
passage 14.
[0078] When the measurement passage 112 is blocked from the intake
passage 14, fuel vapor produced in the fuel tank 32 flows through
the measurement passage 112. The physical quantities correlating to
the fuel vapor state are detected in the measurement passage 112
for measuring the fuel vapor state. Accordingly, the fuel vapor
state can be precisely measured, irrespective of the fluctuation in
negative pressure in the intake passage 14. Here, the components of
the state measuring unit, which includes the pump 42, the solenoid
valve 44, the pressure sensor 50, the ECU 60, the measurement
passage 112, and the like, for measuring the fuel vapor state are
diagnosed. Therefore, when any of the components is malfunction, an
appropriate process such as the malfunction warning, malfunction
recording, or purge suspension can be performed.
[0079] The ECU 60 serving as the diagnosis unit performs the
diagnosis of the pressure detecting unit immediately after starting
the engine 10. Therefore, a malfunction of the state measuring unit
can be found out at an early state, and the appropriate process can
be performed.
Modified Embodiment
[0080] In the first embodiment, the throttle 40 communicates with
the atmosphere through the solenoid valve 44 when supplying
electricity to the solenoid valve 44 is terminated. Alternatively,
the solenoid valve 44 may block the throttle 40 from the atmosphere
when supplying electricity to the solenoid valve 44 is terminated.
In this case, the measurement of the fuel vapor concentration, the
purge and the leak check operation are performed in accordance with
a time chart shown in FIG. 14.
Second Embodiment
[0081] As shown in FIG. 15, the solenoid valve 44 in the first
embodiment may be replaced with solenoid valves 62 and 64. In this
case, the malfunction of the solenoid valve 44 in the first
embodiment may be replaced with a malfunction caused in at least
one of the solenoid valves 62 and 64.
Third Embodiment
[0082] As shown in FIG. 16, the solenoid valve 46 in the first
embodiment may be replaced with solenoid valves 66 and 68. In this
case, the malfunction of the solenoid valve 46 in the first
embodiment may be replaced with a malfunction caused in at least
one of the solenoid valves 66 and 68.
Fourth Embodiment
[0083] As shown in FIG. 17, a fuel vapor treatment apparatus 70
includes a solenoid valve 72 for interrupting the communication
between the first canister 34 and the atmosphere. In the fourth
embodiment, the components for measuring the fuel vapor
concentration are not used for the leak check operation of the
purge system. The time chart of the fourth embodiment as shown in
FIG. 18 depicts only the fuel vapor concentration measurement and
the purge.
Other Embodiments
[0084] The fuel tank 32 may connect with the intake passage 14
through the purge valve 36. In this structure, fuel vapor in the
fuel tank 32 may be purged into the intake passage 14 directly
through the purge passage 102 without intervention of the first
canister 34, while fuel vapor produced in the fuel tank 32 is
adsorbed to the first canister 34. Also in this case, the fuel
vapor concentration in the fuel tank 32 is measured using the state
measuring unit so as to control the purge valve 36 and the
injection quantity of the fuel injection valve 16.
[0085] The pump 42 is used for decreasing pressure in the
measurement passage 112. Alternatively, the pump 42 may be used for
increasing pressure of the measurement passage, in a particular
structure of the state measuring unit for measuring the fuel vapor
concentration.
[0086] An absolute pressure sensor may be used as the pressure
detecting unit.
[0087] The fuel vapor concentration may be measured in accordance
with the air pressure and the mixture pressure. In this case, it is
desirable to control the rotation speed of the pump 42 at a
constant speed. The flow rate in the measurement passage may be
adopted as a physical quantity for measuring the fuel vapor
concentration. A fuel vapor state other than the fuel vapor
concentration may be obtained by measuring the pressure or flow
rate in the measurement passage.
[0088] The second canister 48 may not be provided to the fuel vapor
processing apparatus.
[0089] In the above embodiments, the pump 42 is used for the leak
check operation of the fuel vapor treatment apparatus, in addition
for the measurement of the fuel vapor concentration.
[0090] Alternatively, an additional pump other than the pump 42 may
be employed for performing the leak check operation of the fuel
vapor treatment apparatus.
[0091] The respective functions of the above unit may be
constructed of hardware resources, programs, or a combination of
the hardware resources and programs. The respective functions of
the units are not restricted to ones, which are hardware resources
that are physically independent of one another.
[0092] The above structures of the embodiments can be combined as
appropriate.
[0093] It should be appreciated that while the processes of the
embodiments of the present invention have been described herein as
including a specific sequence of steps, further alternative
embodiments including various other sequences of these steps and/or
additional steps not disclosed herein are intended to be within the
steps of the present invention.
[0094] Various modifications and alternations may be diversely made
to the above embodiments without departing from the spirit of the
present invention.
* * * * *